function A=df2(x);
n=3;
A=zeros(n,n);
A(1,1)=2*x(1)-10;
A(1,2)=2*x(2);
A(1,3)=1;
A(2,1)=x(2)^2;
A(2,2)=2*x(1)*x(2);
A(2,3)=2*x(3)-2;
A(3,1)=2*x(1);
A(3,2)=2*x(2)-3;
A(3,3)=2*x(3);